[oxygold]

Sorry for my last reply, maybe my bad gramme makes you confused.
Let's get this in a clear way. for example: the first time you run the eclipse, there will be a tip for you to select the workspace, isn't it? then when you check that, then the default value will be saved in preference.
Next time while you run eclipse again, eclipse will access to preference to check is there any default value for workspace. If it does, then follow the default instruction, otherwise, popup another dialog to ask you what workspace are you going to choose.